The deaths have sparked renewed interest in potential protections to keep straphangers safe, ranging from laser sensors connected to alarms, to platform screen doors, like the ones seen in some European cities and used on airport shuttles, including the JFK AirTrain.

Subway deaths spiked in 2012, with 55 people killed, up from 47 in 2011 and the highest number of deaths since 2007, according to MTA figures.

But MTA acting executive director Thomas Prendergast said Monday that installing sliding doors would be extremely complicated because the system uses different-sized subway trains with doors in different places and also has some curved and very narrow platforms.

There's also the prohibitive cost of adding sliding doors: an estimated $1 billion, or more than $1.5 million per station, officials said.

“If you look at it in terms of order of magnitude costs and what it would compete against in terms of other safety improvements, it’s a difficult argument," Prendergast told reporters following a meeting of the MTA's transit committee Monday.

"What we know we can do is we can focus efforts right now on trying to change customer behavior, and that’s what we’re doing," he said.

The door idea, however, is still being explored, with a potential pilot project on the L line.

Another idea being mulled by officials is new "intrusion technology," which has previously been used for security. Prendergast envisions using laser sensors to detect whether a person has climbed or fallen onto the tracks.

“You could tie it to an alarm system, flashing lights, things of that nature, to warn people that there was somebody [there],” he said.

The board is currently investigating the technology and would like to develop a pilot to test what could be "a quicker and lower-cost alternative" to the barriers, officials said.

In the meantime, the MTA is ramping up its installation of new “help points” intercoms, which riders can use to report emergencies and call for help. The blue-lit devices, which are now installed in three stations, will be rolled out to 100 stations by the end of 2014, officials said.

The agency is also increasing its public awareness efforts, with new alerts warning riders to stay away from the platform edge appearing in tens of thousands of pamphlets, on subway cars, on the backs of MetroCards, on digital panels, in newspapers and on transit workers' lapel pins.

“We have to re-double our efforts,” Prendergast said.

But one thing not under consideration is an effort by the transit union to slow down trains as they're entering stations.

Board members screened a video of a computer model that predicted slowing trains would badly exacerbate crowding on platforms, creating new, unintended safety consequences as people pushed and shoved.

Of the 141 recorded incidents in which a train struck a person last year, 54 were caused by tripping and falling, 33 happened after people intentionally entered the tracks to retrieve lost items, trespass or cross the tracks, and another were 33 caused by people jumping in a suicide attempt, officials said.

Five of the incidents were the result of someone being pushed or bumped onto the tracks.

About a quarter of the incidents involved drugs or alcohol, officials said.

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